The present invention relates to a device for suppressing the noise emission by a car engine.
An gasoline engine provided in a current car utilizes a discharge in a gap of a plug by high voltage induced on an ignition coil, for providing a spark in a plug of an engine. However, said discharge accompanies an undesired high frequency radio wave noise by the resonant circuit composed of a negative resistance induced by the discharge and the inductance of an ignition coil. Said radio wave disturbs the operation of a broadcast radio receiver by providing an undesired noise.
A prior art for preventing said noise is to insert a resistor in a secondary circuit of an ignition coil circuit. Said reistor operates to neutralize said negative resistance.
However, said prior art has the disadvantages that the spark energy applied to the gap for discharge is reduced since the power consumption in the resistance is large, and that the miss-firing of an engine occurs when the ratio of the gasoline to the air is reduced at the start-up time of an engine and/or the acceleration period of a car. If the value of the resistance is designed small for overcoming said disadvantages, the effect of the resistance for suppressing the ignition noise is also reduced.